The hydraulic pump motor forming the subject of this application comprises a central rotor of the pump motor inside of which hydraulic cylinders are arranged. Hydraulic pistons can move inside these cylinders. When the central rotor rotates relative to the housing of the pump motor, these cylinders are alternately put in a relationship with an internal input-output conduit, then with an external input-output conduit by an input-output distributor constituted either by a cylindrical stator or by an axial stator. To this end this distributor has an internal input-output conduit angular collector central to this rotor which is connected to the internal input-output conduit, and has an external input-output conduit angular collector which is connected to the external input-output conduit.
Oil from the pump motor can therefore pass alternatively from this distributor to this cylinders, then from this cylinders to this distributor via this collectors in particular due to an internal input-output canal of the central rotor which connects each hydraulic cylinder to an input-output orifice of the central rotor which can be placed either facing the input-output angular collector of the internal conduit or facing the input-output angular one of the external conduit.
It is noted that in the U.S. Pat. No. 3,001,775 belonging to the applicant the angular phasing of the input-output distributor relative to the housing of the pump motor is fixed. Now, the conditions of operation of this pump motor can vary in particular in pressure and in the piston swept volume and whether this pump motor is operated in in “pump” mode or in “motor” mode. Each condition of the operation corresponds—for a criterion of the best output of the hydraulic pump motor—to an optimum angular phasing of the input-output distributor relative to the housing of the pump motor.
Consequently, it would be desirable that the phasing of the input-output distributor is variable in particular as a function of the pressure, of the piston swept volume and of the “pump” or “motor” mode under which this pump motor is operating with the objective of optimizing the output of the latter.
The significance of this variable phasing stems in particular from the non-null compressibility of the pump motor oil implemented in this pump motor. In fact, this compressibility brings about non-recoverable work losses when there is a significant separation of pressure between on the one hand an internal canal of input-output of the central rotor connected to a hydraulic cylinder and on the other hand the input-output angular collector of the internal or external conduit at the moment at which this internal canal is placed in rotation via its input-output orifice of the central rotor with this collector.
In fact, when this canal is related to this angular collector, if the pressure prevailing in this canal is greater than the one prevailing in this collector, the pump motor oil contained in this canal is relaxed in this collector without producing work in such a manner that the compression energy of the pump motor oil is dissipated in the form of heat without being able to be converted into useful work by the central rotor of the pump motor.
It is the same if the pressure prevailing in the input-output angular collector of the internal or external conduit is greater than the one prevailing in the internal input-output canal of the central rotor at the moment at which the latter is placed in a relationship with this connector.
For a given pressure and a piston swept volume of the hydraulic pump motor according to the application of the U.S. Pat. No. 3,001,775, a single phasing of this angular collectors relative to the housing of the pump motor permits this pump motor to deliver its best delivery when this pump motor is operating in the “pump” mode while a single other phasing of this connectors gives this pump motor the best possible delivery when the latter is operating in the “motor” mode.
In order to obtain a maximum delivery from the pump motor according to the application of U.S. Pat. No. 3,001,775, it would be required that the angular sector occupied by the input-output angular collectors of the internal and external conduits are variable and it would also be required that the angular position of these connectors relative to the pump motor housing would be variable.
Unfortunately, it is difficult or even impossible in practice to vary the angular sector occupied by the input-output angular collectors of the external conduit just as it is difficult or even impossible to vary the angular position of each of these collectors relative to the pump motor housing independently of each other. This is due to the fact that this angular sectors are arranged in the input-output distributor that is constituted by one and the same piece.
On the other hand, subject to the necessary means being provided, it would be a priori possible to vary the angular position of the input-output distributor relative to the pump motor housing. This additional function, which is not provided in the U.S. Pat. No. 3,001,775 would permit in particular providing for the input-output distributor an angular position when the hydraulic pump motor is operating in “pump” mode different from the one retained when this pump motor is operating in the “motor” mode. This angular position could also be determined by the pressure and/or the piston swept volume under which the hydraulic pump motor is operating or by any other parameter, whatever its nature. This would result in a substantial gain of delivery and of efficiency for the pump motor according to the U.S. Pat. No. 3,001,775.